Histopathology of hypotrichosis with juvenile macular dystrophy

Hypotrichosis with juvenile macular dystrophy (HJMD) (MIM 601553) is a rare disorder characterized by the paucity of hair and progressive macular degeneration leading to blindness. We have recently shown that mutations in the CDH3 gene encoding P-cadherin are the proximal cause of HJMD. The present study was performed to establish the histopathology of this disorder. 4 mm punch scalp biopsies from 6 HJMD patients aged 9 to 21 years were studied. All patients had a homozygous missense mutation resulting in a single amino acid substitution at position 503 of P-cadherin amino acid sequence (R503H). The total number of hair follicles varied between 6 and 14 per histologic section. More catagen-telogen hair follicles were observed in five cases, and an increased ratio of vellus hair follicles to terminal hair follicles was observed in two cases. There were no signs of inflammation or scarring. Thus, the most frequent histologic abnormality in HJMD resembles chronic telogen effluvium. This suggests that absence of functional P-cadherin interferes with normal hair cycle.